1. Field of the Invention
The present invention relates to an optical image measurement device configured to apply a low coherence light beam to a measurement object and form an image of the surface morphology or internal morphology of the measurement object by using a reflected light or a transmitted light.
2. Description of the Related Art
In recent years, attention has been focused on an optical image measurement technology of forming an image showing the surface morphology or internal morphology of a measurement object by using a light beam from a laser light source or the like. Because this optical image measurement technology does not have invasiveness to human bodies unlike an X-ray CT device, it is particularly expected to further use this technology in the medical field.
Japanese Unexamined Patent Application Publication JP-A 11-325849 discloses an optical image measurement device having a configuration that: a measuring arm scans an object through a rotary deflection mirror (Galvano mirror); a reference mirror is disposed to a reference arm; an interferometer is used at the outlet so that the intensity of light appearing from interference of light fluxes from the measuring arm and the reference arm is analyzed by a spectrometer; and a device gradually changing the light flux phase of the reference light in non-continuous values is disposed to the reference arm.
The optical image measurement device of JP-A 11-325849 uses a method of so-called “Fourier Domain Optical Coherence Tomography (OCT)” based on technology of German Patent Application Publication DE4309056A1. In other words, it is image creation of a morphology of an object to be measured depthwise by the following steps: irradiating the object to be measured with a low-coherence light beam; dispersing (spectral resolving) an interference light that is based on the reflected light thereof; detecting the spectral intensity distribution thereof with a light detector such as a CCD; and carrying out Fourier transformation of the detection results. Herein, the interference light generated from a signal light and a reference light is adapted to be guided by an optical fiber (light guiding part) to exit from a fiber end, spectrally resolved with a diffraction grating or the like, and detected by the light detector.
Furthermore, the optical image measurement device described in JP-A 11-325849 is provided with a Galvano mirror that scans with an optical beam (signal light), whereby it is possible to form an image of a desired measurement region of a measurement object. Because this optical image measurement device is configured to scan with a light beam only in one direction orthogonal to the depth-direction, a formed image is a 2-dimensional cross-sectional image of the depth direction along the light beam scanning direction.
Besides, Japanese Unexamined Patent Application Publication JP-A 2003-543 discloses a configuration in which the aforementioned optical image measurement device is applied to the field of opthalmology.
For such an optical image measuring device, the positional relationship between the position of the fiber end of the optical fiber that guides the interference light and the light detector that detects the interference light that has been spectrally resolved is important. In other words, when intervened by a misalignment in the positional relationship between them, the interference light that has been spectrally resolved is no longer properly irradiated on the light-receiving surface of the light detector, so it may not be capable of properly forming an image because the light detector cannot receive the interference light or the amount of light received by the light detector becomes insufficient.
For traditional optical image measuring devices, when the positional relationship between the fiber end and the light-receiving surface of the light detector is disturbed, the user manually adjusts the position of the fiber end or the position of the light detector, or a serviceman from a maintenance service company is called out to adjust the position.
In this way, for traditional optical image measuring devices, there is a problem in that the alignment between the fiber end and the light-receiving surface has to be carried out, requiring substantial labor or time.
In addition, the suitability of the positional relationship between the fiber end and the light-receiving surface is revealed only after a measurement has actually been conducted, so it may not be capable of obtaining an image at the timing when the user desires.
Moreover, because the fiber end surface is minute (i.e. a diameter of only approximately a few μm) the alignment between the fiber end and the light-receiving surface of the light detector needs to be carried out very precisely. In addition, a line sensor is often used as the light detector, but the width of the line sensor is typically approximately from a few μm to less than 20 μm, so it is required that the alignment be carried out particularly precisely widthwise. Meanwhile, the positional relationship between the fiber end and the light-receiving surface is easily altered by a shock to the device housing, environmental conditions such as temperature or humidity, or the like. Therefore, for traditional optical image measuring devices, precise alignment between the fiber end and the light-receiving surface has to be conducted at a considerable frequency.